<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    let num1=10
    let num2=20
    let temp // 临时变量

    temp=num1
    num1=num2
    num2=temp
    console.log(num1)
    console.log(num2)
</script>
</body>
</html>